Transcript Minerals and Rock Resources

Chapter 12
Minerals and Rock Resources
Figure 12.2
Ore Deposits
• Ore – rock in which a valuable or useful
metal occurs to be economic to mine
• Concentration Factor (CF): CF = Cm/Cmc
– Cm = Concentration factor of the metal in the ore
– Cmc = Concentration of the metal in average
continental crust
• The higher the CF - the richer the ore
Examples of Metals obtained from Ores
• Aluminum or Iron – appliances and
vehicles
• Metals for conductors or semi-conductors
• Gems, gold, and silver – jewelry
• Lead from galena
• Copper from malachite and azurite
• Zinc from sphalerite
• Many other metals found in rocks
Figure 12.1
Cost Factors
• Concentration Factor (CF)
• 4 to 25,000 times CF
– highly variable occurrences
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World demand and many market factors
Energy cost
Human/labor cost
Distance to processing or market
Environmental cost - remediation
Distribution
• Globally, very un-even distribution
– Some countries have plenty – export nations
– Some countries have none – import nations
– Figure 12.1
• Un-even distribution is reason wars are
fought
Figure 12.6 a
Figure 12.6 b
Types of Mineral Deposits
• Igneous Rocks and Magmatic Deposits
– Pegmatite
– Kimberlite
• Hydrothermal Ores
– hydrothermal
• Relationship to Plate Margins
• Sedimentary Deposits
– Banded iron formation
– Evaporite
• Other low-temperature ore-forming processes
– Placers
• Metamorphic Deposits
Figure 12.3
Figures 12.4 a, b, and c
Figure 12.5
Figures 12.7 a and b
Figure 12.8
Figure 12.9
Figure 12.10 a and b
Mineral and Rock Resources
Examples (the ways we use)
• Metals – iron, aluminum, copper, lead,
zinc, nickel, cobalt, gold, silver, or platinum
• Nonmetallic Minerals – sulfides, lime
(calcium carbonate), sulfur, halite, clay,
gypsum, or potash
• Rock resources – most abundant quantity
of earth resources we use
– Sand, gravel, limestone, quartz-rich sand,
marble, granite, and sandstone
Mineral Supply and Demand
• Global demand is always growing
– About 2% pre-World War II for most metals
– About 10 % World War II to mid-1970’s
– Demand is fluctuating now
• U.S. Mineral Production and Consumption
– U.S. population is only 4.5% of the world but
consumes many times its share of the world
supply
Figure 12.11
Figure 12.12
Figure 12.13
World Mineral Supply
• World demand is always fluctuating
• Commodities do not follow fluctuating
trends
• Mineral reserves eventual will be depleted
• Import/export relationships will fluctuate
• Technology often allows more access to
difficult or low grade ore deposits
• Future mineral-resource shortages will
occur and cause international tension
Figure 12.14
Table 12.2
Minerals for the Future
Some Options Considered
• Consider controlling consumption rates
– Reduce the consumption rates (unlikely)
– Hold these rates steady (unlikely)
• Carefully consider the facts:
– Globally the less developed nations are striving
to achieve comparable standards of living as
the technologically advanced countries enjoy
– Countries that have the fastest-growing
populations are not well endowed with mineral
deposits and are the less developed countries
of the world!
Figure 12.15
New Methods in Mineral Exploration
• Fact: the economically easy and profitable
deposits are being depleted
• Geophysics is a useful aid to locating new
deposits
– Gravity survey
– Magnetic survey
– Electrical property survey
• Geochemical survey and prospecting is an
increasingly popular exploration tool
• Remote sensing is expanding into
exploration strategies
Figure 12.16
Remote Sensing
• Sophisticated but valuable exploration tools
• Useful to detect, record, and analyze energy
emitted off the earth
– Aerial photography
– Satellites
– Space shuttle, and other manned missions
• Remote sensing is backed up by ‘ground truth’
activities
– old fashioned geologic mapping
• Advances in the geological sciences are
directed toward intigration of remote sensing,
geochemistry, and geophysics
Figures 12.17 a and b
Figure 12.18
Marine Mineral Resources
• Oceans – our new mineral frontier
• Sea water contains abundant dissolved minerals
and many useful element
– Most extraction techniques currently used are energy
intensive and expensive
• Hydrothermal ore deposits along seafloor
spreading ridges are a possible source of many
materials
– Currently, they are too deep - of limited benefit
• Manganese nodules are widely distributed on
the ocean floors; a promising solution.
– Many political, environmental, and legal obstacles
must be over come before they can be mined
Fig. 12.19
Fig. 12.20
Conservation of Mineral Resources
• Overall need for resources is growing – must
reduce this expansion
• Some mineral resources maybe substituted by
other, more abundant resources
– Plastics replacing automobile parts
• Recycling – many metals are successfully
recycled
– More recycling is required
– Not all commodities are easy to recycle
• Measures to reduce demand must be the key
Figure 12.21
Impacts of Mining Activities
• Mining and mineral-processing activities can
modify the environment in various ways
• Both underground mines and surface mines
have their own sets of associated impacts
• Safety, hazards, and water and air pollution
should not be overlooked
• Very stressful to the environment
– Must be carefully planned
– Must be safe to miners and their neighbors
– Must be contained – water and air pollution is a
major problem
Figure 12.22
Underground Mines
• Generally hard to see where they are located
– Area of disturbance is local
• Miners place the tunnels close to the ore body to
cut down on waste
• Once mines are closed they can be sealed with
the non-ore rock (waste rock)
• Surface collapse general limited and controllable
with modern mine reclamation practices
– Old, abandoned, and forgotten mines are still
a problem
Fig. 12.23
Surface Mines
• Quarrying extracts rock to be used either intact
(building blocks or facing stone) or crushed
(cement-making and road bed)
• Open-pit
– Mine a large ore body located near the surface
– Permanent changes to local topography will occur
• Strip mining
– Most ores occur in a layer that generally is parallel to
the surface
– The ore zone is overlain by vegetation, soil, non-ore
rock that must be removed
– Spoils banks are designed to collect the waste rock
– Current reclamation law requires that it be return to
the pit and the original soil replaced
– Expensive but vital
Fig. 12.24
Fig. 12.25
Mineral Processing
• Mineral extraction is environmental hazardous
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Ore rock is ground or crushed for extraction
The fine waste material is placed in tailings
The tailings are exposed to wind and weather
Harmful elements such as mercury, arsenic,
cadmium, or uranium can leached out
– The surface and subsurface water systems are too
often contaminated
– Chemicals used in ore extraction must be controlled
and not just dumped
– Smelting ores to extract metals, often produce metal
laden exhaust gas or ash, sulfur oxid,e and acid rain
pollution
Fig. 12.26